1. Technical Field
The present invention is related to pixel data output, more specifically to a method and an apparatus for outputting pixel data with appended data.
2. Description of the Related Art
By mounting a small or thin imaging device on a small or thin portable terminal, such as a portable phone or a PDA (personal digital assistant), the portable terminal can now function as an imaging device also. Thanks to this new development, the portable terminal, such as the portable phone, can send not only audio information but also visual information. The imaging device has been also mounted on a portable terminal such as the MP3 player, besides the portable phone and PDA. As a result, a variety of portable terminals can now function as an imaging device, capturing an external image and retaining the image as electric data.
Generally, the imaging device uses a solid state imaging device such as a charge-couple device (CCD) image sensor or a complementary metal-oxide semiconductor (CMOS) image sensor.
FIG. 1 illustrates a simple structure of a typical imaging device, and FIG. 2 illustrates general Bayer mosaic filter patterns.
As illustrated in FIG. 1, the imaging device, which converts an external image into an electric data and displays the electric data on a display unit 150, includes an image sensor 110, an image signal processor (ISP) 120, a back-end chip 130, a baseband chip 140 and the display unit 150. Besides, the imaging device can further have a memory, storing the converted electric data, and an AD converter, converting an analog signal into a digital signal.
The image sensor 110, which has a Bayer pattern, outputs an electrical signal corresponding to the amount of light inputted through a lens, per unit pixel. To detect the color of an image exposed to the image sensor 110, the pixel of the image sensor 110 is covered by a color filer that absorbs the light wavelength of all colors except for the color of the color filter. Color information is generally extracted by arranging a color filter array on the pixels of the image sensor 110. FIG. 2 illustrates a Bayer mosaic filter, which is the most general type of the color filter array. The Bayer mosaic filter has a checkerboard-like shape and consists of alternating rows of red (R), green (G), and blue (B) filters. The red and green filters are offset to each other such that two green filters cannot share an edge area between an adjacent low and column. Interpolation, based on the color intensity of surrounding pixels, is required to take complete color information of each pixel.
The image signal processor 120 converts raw data inputted from the image sensor 110 into a YUV value and outputs the converted YUV value to the back-end chip 130. Based on the fact that the human eye reacts more sensitively to luminance than to chrominance, the YUV method divides a color into a Y component, which is luminance, and U and V components, which are chrominance. Since the Y component is more sensitive to errors, more bits are coded in the Y component than in the U and V components. A typical Y:U:V ratio is 4:2:2.
By sequentially storing the converted YUV value in FIFO, the image signal processor 120 allows the back-end chip 130 to receive corresponding information.
The back-end chip 130 converts the inputted YUV value to JPEG or BMP through a predetermined encoding method and stores the YUV value in a memory, or decodes the encoded image, stored in the memory, to display on the display unit 150. The back-end chip 130 can also enlarge, reduce or rotate the image. Of course, it is possible, as shown in FIG. 1, that the baseband chip 140 also receives from the back-end chip 130, and display on the display unit, the decoded data.
The baseband chip 140 controls the general operation of the imaging device. For example, once a command to capture an image is received from a user through a key input unit (not shown), the baseband chip 140 can make the back-end chip 130 generate encoded data corresponding to the inputted external image by sending an image generation command to the back-end chip 130.
The display unit 150 displays the decoded data, provided by the control of the back-end chip 130 or the baseband chip 140.
With today's increasing number of pixels and decreasing size of the image sensor 110, it has become insufficient for the captured and outputted raw data to process an image.
That is, since recent image processing technologies include various methods such as the 7×7 interpolation, a lot of appended data are required in the left, right, upper and lower areas to properly output processed raw data to the display unit 150. This is for preventing a loss of real data to be processed and displayed.
The conventional image processing technologies perform an image process regardless of the appended data. Accordingly, the image has not been displayed properly on the display unit, and the left, right, upper and lower borders were lost like a picture frame. This may be because the default appended data is smaller than the data size required for image processing such as the interpolation.